Why Do Birds Have Feathers And Bird Colours
Birds and Feather Colour
Feathers are unique to birds and apart from creating an ability to fly the feathers have other uses which include insulation, floatant properties and certain types such as those on the tail of woodpeckers and Oxpeckers are stiff to act as a counterpoint when balancing on vertical or near vertical surfaces.
In exploring the colour of birds a little bit of physics helps.
Light as we see it normally is not what it truly is. To see light as it
really appears is to view a rainbow. The myriad of colours produced in a
rainbow is the light spectrum of colours and there are many colours but
the basis for all the colour variations in simple terms are mixtures of
red green and blue in different proportions.
When light falls on any object the colour we see is the remains of those colours NOT absorbed by the object. In other words if an object cannot absorb red but can absorb all other colours by virtue of the pigments used then that object will appear as RED. The red spectrum portion not absorbed is reflected to our eye. The colours we see are the results of absorbed colours being SUBTRACTED from the spectrum.
All naturally occurring substances have an ability to absorb certain wavelengths of light and not others. Pigments are the best examples of substances that absorb different light wavelengths. Mixing pigments therefore can create interesting effects and this is the basic reason along with the way light can scatter or reflect why some birds are splendid in terms of their colours while others are drab.
Feathers and bills are based on a protein called keratin just as our own fingernails and hair are built upon this same protein ... some keratin structures are transparent as in fingernails while others are not as in different colours of hair).
Nearly all birds have feathers containing either or both carotenoid pigments or melanin pigments as well as keratin. Melanin is a black pigment while carotenoids are yellow, red, orange pigmentations. Carotenoid pigments are a function of diet to a large extent.
If you understand this then it is relatively easy to explain why birds have certain colours and why the colours are distributed in the way they are. For example if different feathers contain different pigments and types or amounts of keratin then those feathers will have different colours because each type of feather will absorb different wavelengths of light leaving only certain other colours to reflect.
If a bird lacked melanin then it would be white with red eyes and pink
legs. This is called albinism.
This is an oversimplified version and does not explain why colours seem
to change based upon direct sunlight or muted shade. However it is
sufficient to allow us to appreciate the wonder of nature and the beauty
It also makes the hobby of bird watching very interesting at times
because what the books say a bird should look like is not necessarily
true because of minor pigmentation variations. This is seen a lot in
raptors. Maybe it's the reason I struggle to identify these birds.
It does leave the question as to why colours change in certain birds during mating periods? ...
Info obtained from www.birdsinsa.com